Nurse

She was a student faculty member at the school in 1971 and apparently knew Headmaster who was also a student at that time. She was involved in stopping the spread of Chemica Desin and explained to Ian the history of the chemical.

She is currently the school nurse at Tower Prep and runs the infirmary. She and Headmaster later asked Ross Anderson to show them how she had modified Chemica Desin. ("Election")

Ian witnessed Nurse in a lab in West Campus where she (presumably with the help of Ross Anderson) developed a new version of Chemica Desin: Chemica Desin 2.0. Conner Owens managed to steal a vial of the chemical from her lab, but it was later recovered. The purpose of this substance and her reasons for creating it are unknown. ("Snitch")

Theories

She could be the seventh person who knows that headmaster is secretly working to restore the school to a positive force because she and headmaster worked secretly with ross anderson to develop chemica desin 2.0 which could possibly be used to overthrow the board of directors whom Headmaster is secretly fighting against.